The general objective of this Program of projects is to investigate the mechanisms operative in the action of hormones as well as prostaglandins in the uterus in various functional states as influenced by steroid hormones. The central theme is the hypothesis that cyclic AMP and perhaps other cyclic nucleotides play a "key" regulatory role in the informational transactions which occur between the cell and chemical signals in the environment, be they hormones (eg. oxytocin) regulatory metabolites (eg. prostaglandins) or drugs. The information obtained may lead to new insights for fertility control. For 1973, the specific objectives related to three main areas: 1. Role of Cyclic Nucleotides in Uterine Contractility: Parameters affecting metabolism of cyclic AMP (adenyl cyclase, phosphodiesterase, and flow of radioactivity from labeled ATP pools into cyclic AMP pools) will be studied in uteri of castrate rats treated with estrogens and progestins, alone and in combination. 2. Isolation of Oxytocin Receptor: a) Synthesis of analogues of oxytocin to approach receptor isolation by affinity chromatography and affinity labeling; b) Modes of coupling of neurohypophyseal hormone receptor to renal medullary adenyl cyclase will be explored in detail; and c) An oxytocin receptor assay will be developed to study variation of abundancy of this receptor in myometrium. 3. Biochemistry of Uterine Contraction: The molecular characteristics of the myometrial sarcoplasmic relaxing system will be studied in rabbit and rat uteri under the influence of various steroid hormones.